1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to an exposing method in which different kinds of aligning and exposing apparatuses are used.
2. Description of the Related Art
As a semiconductor technology develops, the integration of semiconductor devices continues to increase. This means that the number of semiconductor devices integrated into the area of a substrate, that is, the density of semiconductor devices, increases, and that the distance between the semiconductor devices becomes narrower.
Semiconductor devices are formed on a substrate by a photolithography process and an etching process. In the photolithography process, a pattern to be formed is transferred onto the substrate. The photolithography process can be divided into a step of coating the substrate with a photosensitive film, an aligning and exposing step of aligning an exposing apparatus with respect to the coated photosensitive film and exposing the photosensitive film, and developing the exposed photosensitive film. A mask pattern is formed by the development step. In the etching process, a material film formed on the substrate is patterned using the mask pattern as an etching mask. By doing so, the pattern defined on the substrate by the mask pattern is transferred onto the substrate.
It can be seen that in the above processes the characteristics of the pattern formed on the substrate, for example, the line width of the pattern and the distance between the patterns are already determined in the process of forming the mask pattern. This is because the etching process is only a process of transferring the pattern etched into the mask pattern to the material film formed on the substrate using the formed mask pattern as an etching mask.
Therefore, increasing the integration of the semiconductor devices requires narrowing the width of the pattern formed in the mask pattern and the distance between the patterns in the process of forming the mask pattern.
The characteristics of the mask pattern are determined in the aligning and exposing step. In this step, the characteristics of the pattern formed in the mask pattern can be affected by the characteristics of the photosensitive film or the environment. However, the characteristics of the pattern are affected more by the aligner and exposer apparatuses used for alignment and exposure. Also, since overlap precision or the resolution of the exposer can vary according to an aligning and exposing method even though the same aligner and exposer apparatuses are used, the characteristics of the pattern are significantly affected by the aligning and exposing method.
Different types of aligning and exposing methods include a contact method, a proximity method, a reflective-type projection method, and a reducing projection lens method. Among the above methods, the contact method and the proximity method are restrictively used only in a process where there is some room in an overlap margin, due to problems caused by the contact of the mask pattern to the photosensitive film and problems resulting from resolution deterioration due to a diffraction phenomenon.
The reflective-type projection method and the reducing projection lens method, which are scan methods, or step and repeat methods, are widely used, since the overlap precision and the resolution are higher than in the contact method and the proximity method. However, as semiconductor devices become more highly integrated, the resolution and the overlap precision required by a design rule exceed the resolution and the overlap precision of the aligner and exposer apparatuses used for the reflective-type projection method and the reducing projection lens method. Accordingly, an aligner and an exposer having higher resolution and overlap precision than those of the aligner and exposer apparatuses used for the reflective-type projection method and the reducing projection lens method are required. Accordingly, production costs of the more highly integrated semiconductor devices are expected to increase, as the effectiveness and efficiency of the aligner and exposer apparatuses used for the reflective-type projection method and the reducing projection lens method are diminished by the increased design rule demands.
To solve the above problem, it is an object of the present invention to provide an exposing method by which production costs of highly integrated semiconductor devices are minimized by the effective and efficient use of conventional aligning and exposing apparatuses.
Accordingly, to achieve the above object, there is provided an exposing method which comprises a photolithography process of forming a material layer on a substrate, coating the material layer with a photosensitive film, and patterning the photosensitive film to restrict the material layer, in order to form a material layer pattern having a desired shape on the substrate, wherein the photosensitive film is patterned using aligning and exposing apparatuses selected from different kinds of aligning and exposing apparatuses, each having different exposing characteristics according to the specific requirements of the particular material layer pattern.
For example, in manufacturing a semiconductor device according to the present invention, where the material layer pattern is an interlayer dielectric film including a contact hole, the photosensitive film pattern formed to restrict the contact hole on the interlayer dielectric film can be formed using a stepper type aligning and exposing apparatus. Where the material layer pattern is a pad layer connected to the substrate through the contact hole formed on the interlayer dielectric film, the photosensitive film pattern formed to restrict the pad layer can be formed using a scanner type aligning and exposing apparatus having an exposing characteristic less precise than the exposing characteristic of the stepper type aligning and exposing apparatus. To provide compatibility, the photosensitive film pattern for restricting the contact hole is formed using a mask including the alignment characteristic of the scanner type aligning and exposing apparatus. Likewise, the photosensitive film pattern for restricting the pad layer is formed using a mask including the alignment characteristics of another aligning and exposing apparatus. The alignment key of the scanner type aligning and exposing apparatus is engraved on the mask of the stepper type aligning and exposing apparatus. Stepper type aligning and exposing apparatuses having different reducing projection ratios are used as one selected from the different kinds of aligning and exposing apparatuses. At least two-stepper type aligning and exposing apparatuses having different reducing projection ratios are selected from the group consisting of stepper type aligning and exposing apparatuses whose projection ratios are 1:1, 2.5:1, and 5:1. The stepper-type aligning and exposing apparatus and the scanner type aligning and exposing apparatus are used as the different kinds of aligning and exposing apparatuses. The stepper-type aligning and exposing apparatus used is one selected from the group consisting of stepper-type aligning and exposing apparatuses whose projection ratios are 1:1, 2.5:1, and 5:1.
According to an embodiment of the present invention, the different kinds of exposing apparatuses selected to be used for a photolithography process are preferably determined by the following evaluation steps:
(a) resolution and precision capabilities of each aligning and exposing apparatus to be used for the photolithography process is assessed; (b) design rule and the overlay margin requirements of a layer to be formed by the photolithography process are investigated and evaluated; (c) aligning and exposing apparatus for the layer to be formed is selected on the basis of the ability of the aligning and exposing apparatus, the investigation, and the evaluation.
Based on the selected aligning and exposing apparatuses, a mask (or a reticle) to be used for the photolithography process is manufactured. Alignment keys for each different kind of aligning and exposing apparatus are all included in the manufactured mask.
Preferably, the mask should be manufactured so that image matching between the different kinds of aligning and exposing apparatuses can be performed. The largest scribe line between those of the different kinds of aligning and exposing apparatuses should be adopted as a scribe line. A wafer array preferably is adopted so that alignment can be performed between the different kinds of aligning and exposing apparatuses.
In the present invention, different kinds of aligning and exposing apparatuses having different exposure capabilities are used in the photolithography process. It is possible to select a suitable aligning and exposing apparatus for each layer to be formed by manufacturing the mask used for exposure to be compatible with different kinds of aligning and exposing apparatuses. By doing so, it is possible to use an aligning and exposing apparatus having a relatively less precise exposure characteristics together with an exposing apparatus having high resolution and alignment precision. Therefore, it is possible to reduce the necessity of additionally introducing an aligning and exposing apparatus having excellent exposure characteristics. In this manner, a high production cost structure is replaced with a low production cost structure, and the utility and productivity of the retained aligning and exposing apparatuses are maximized.